Drinking Iced Tea Raises Kidney Stone Risk: Study

Kidney stones affect about 10 percent of the U.S. population, researchers say

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Researchers from Loyola University Medical Center explained that the popular summertime drink contains high levels of oxalate, a chemical that leads to the formation of small crystals made of minerals and salt found in urine. Although these crystals are usually harmless, the researchers cautioned they can grow large enough to become lodged in the small tubes that drain urine from the kidney to the bladder.

"For people who have a tendency to form the most common type of kidney stones, iced tea is one of the worst things to drink," Dr. John Milner, an assistant professor in the department of urology at the Loyola University Chicago Stritch School of Medicine, said in a news release. "Like many people, I enjoy drinking iced tea in the summer, but don't overdo it. As with so many things involving a healthy lifestyle, moderation is key."

Being dehydrated is the most common cause of kidney stones, the study authors pointed out. Drinking iced tea, however, can increase people's risk for the condition.

"People are told that in the summertime they should drink more fluids," Milner said. "A lot of people choose to drink more iced tea, because it is low in calories and tastes better than water. However, in terms of kidney stones, they might be doing themselves a disservice."

Men are four times more likely to develop kidney stones than women. That risk jumps significantly for men over the age of 40. The researchers noted, however, that postmenopausal women with low estrogen levels and those who have had their ovaries removed are also at greater risk.

To reduce the risk of kidney stones, the researchers advised people to stay hydrated. Although drinking water is best, they noted real lemonade is another good option. "Lemons are high in citrates, which inhibit the growth of kidney stones," explained Milner.

The study authors also advised that people at risk for kidney stones should take the following steps:

Avoid foods with high levels of oxalates, including spinach, chocolate, rhubarb and nuts.

Reduce salt intake.

Eat less meat.

Get enough calcium, which reduces the amount of oxalate absorbed by the body.

Although hot tea also contains oxalates, the researchers noted it's hard to drink enough to cause kidney stones. They added that people who do develop kidney stones that drink iced tea should have their doctor check to see if they are producing too many oxalates.